Author: Lanza, G.
Paper Title Page
WEPPD015 Saturation Behaviour of the LHC NEG Coated Beam Pipes 2525
  • G. Bregliozzi, V. Baglin, J.M. Jimenez, G. Lanza, T. Porcelli
    CERN, Geneva, Switzerland
  In the CERN Large Hadron Collider (LHC), about 6 km of the UHV beam pipe are at room temperature and serve as experimental or utility insertions. TiZrV non-evaporable getter (NEG) coating is used to maintain the design pressure during beam operation. Molecular desorption due to dynamic effects is stimulated during protons operation at high intensity. This phenomenon produces an important gas load from the vacuum chamber walls which could lead to a partial or total saturation of the NEG coating. To keep the design vacuum performances and to schedule technical interventions for NEG re-activation, it is necessary to take in account all these aspects and to regularly evaluate the saturation level of the NEG coating. Experimental studies in a typical LHC vacuum sector were conducted in order to identify the best method to assess the saturation level of the beam pipe. Partial saturation of the NEG was performed and the effects in the variations of pressure reading, effective pumping speed, transmission and capture probability are analysed. Finally, based on these results, a detailed analysis of the NEG coating saturation level of some area of the LHC is presented and analysed.  
WEPPD018 LHC Beam Vacuum During 2011 Machine Operation 2534
  • G. Lanza, V. Baglin, G. Bregliozzi, J.M. Jimenez
    CERN, Geneva, Switzerland
  During the year 2011 the LHC operated for 682 fills, meaning 247 days and 2 hours of stable beam in total. From 368 bunches per beam at 150 ns bunch spacing circulating in the ring in December 2010, the 2011 proton physic ended with 1380 bunches per beam circulating with 50 ns bunch spacing. The machine performances increased in parallel with the vacuum improvement thanks to a well performed scrubbing run in April 2011 and a continuous conditioning of the beam pipes while the machine was running. The 2011 LHC operation ended with one month of ions physic runs. During the machine operation various phenomena of beam - vacuum interaction were detected, analyzed and solved. This paper describes the pressure behavior along the machine layout and mainly in specific components position like TDI and MKI. The “pressure spike” phenomena near the experiment CMS and in some Dipole 1 (D1) regions are discussed. Finally, results obtained during the 25 ns machine developments are presented.